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So when one of Badyaev’s undergraduate students, Clayton Addison, noticed that the male finches on campus in central Tucson were not singing a rapid trill that’s essential for attracting females in the nearby desert, the lab was able to dig into the data for answers. Comparing the beak sizes, bite forces, and diets of the two populations, the researchers showed that the urban finches rely so heavily on feeders that their beaks have adapted: they’ve become longer and deeper to accommodate the sunflower seeds typically on offer, which are much larger and harder than the small cactus and grass seeds that rural finches eat. This adaptation has altered not only how urban males sing, but also what urban females prefer in a mate. It’s a pattern that Badyaev has since found in other places where finches live in the shadow of humans, the same large beaks arising from a surprisingly diverse array of developmental pathways. Such varied routes to an identical end—a beak strong enough to crack sunflower seeds—may be one way that nature hides variability from the swinging axe of natural selection.

Evolutionary theory aside, however, I was stuck on one point: There’s such a thing as a finch Brooklyn accent—thanks to feeders like mine.